Xmpl2d59, 59th 'example' data file for CPO2D

Single atom ion source.


The dimensions and voltages used here might be quite wrong (we do not know much about this subject) -this data file is provided only to illustrate a possibility for the design of a single-atom ion source, so that it can be used as a template for a realistic simulation. Only a small number of segments has been used.

The single atom tip is the sharp end of a cone of height 2.5e-5mm and base radius 1.5e-5mm, that sits on a hemisphere of radius 1e-3mm.

The cone is divided into 10 segments and is specified as a thermionic cathode that has kT = 0, but only the 3 segments nearest to the tip are specified as being active. One cathode ray starts from the centre of each of those 3 segments. The ‘particle type’ has been specified as mass 3AU, charge +e, and so is Li+. No attempt at iteration has been made to study any effects of space-charge. The beam is attracted to the end plate by a potential of -10V.

The 'advanced' option for step lengths is used to give small steps near the tip but larger steps further out.

Note that for some of the electrodes it is necessary use the 'advanced' option to 'concentrate' the segments.

A beam-forming ring has been added to try to push the beam into the forward direction. Although the radius and width of this ring have been approximately adjusted, this has not been done systematically and no attempt has been made to adjust the shape and position of the ring.